The broad objective of the planned research is to improve clinical decision making with respect to the non-operative treatment of adolescent idiopathic scoliosis (AIS). Bracing (the use of a spinal orthosis) is the standard of non- operativ care for children at high-risk for continued progression of scoliotic curvatures. The Bracing in Adolescent Idiopathic Scoliosis Trial has enrolled a representative cohort of 384 high-risk subjects being treated either by bracing or by watchful waiting across 25 participating institutions. Treatment assignment was via randomization for 40% of subjects and based on preference for the remainder. The renewal of this project will allow continued follow-up of all subjects to defined radiographic and skeletal maturity endpoints. The remaining subjects are anticipated to exit the study in Years 1 and 2 of this renewal; Year 3 will be devoted to finalization of the datasets, data analyses, and manuscript preparation. The specific aims of BrAIST are to 1) compare the risk of curve progression to surgical threshold (e 50 degrees) in subjects treated by a brace to those treated by watchful waiting, 2) compare health and functioning, quality of life, and self- image over time in the two treatment groups, 3) determine the relationship between bracing dose (wear time) and curve response, and 4) to develop a predictive model for curve progression based on individual patient characteristics at initial presentation, and based on these characteristics, to estimate degree of risk reduction associated with the use of a brace. Clinical decision making will be improved by translation of these results into evidence-based prognosis and estimates of how the prognosis, specifically the risk of progressing to surgery, may be altered by the use of bracing.